Achieving certified safety in explosive atmospheres with flexible motors and drives packages

Explosive atmospheres present unique challenges and difficulties. Fortunately, they are now easier to manage with the right combinations of drives and motors.  

Explosions may occur in virtually any process where air is mixed in the right concentration with flammable gasses, mist, vapors or dust. All that is needed is a source of ignition to be present at the same critical time. The risk of such explosions is known to be present in a broad range of industries, including oil and gas, food and beverages, chemicals, water and waste water treatment, waste handling, agriculture and wood processing.

In the food and beverage industry, for example, storage facilities like grain silos often contain high levels of dust mixed with air. If motors there become overheated for any reason, which can be as simple as the wrong type of drive being selected to control motor speed, they can detonate dangerous explosions. For the ignition source, it is clear that a spark is not always required to start the fire or explosion; a hot motor alone is sufficient under the right conditions.

Various ways to meet Ex standards most efficiently

Ensuring safe operation of processes in a potentially explosive atmosphere requires careful adherence to explosion-safety standards. To help meet these standards, the ‘Ex’ safety designation has been created to indicate that the motor is considered safe to use in a designated explosive atmosphere. Ex certified motors, therefore, must be selected for applications in potentially hazardous areas. In addition, it should be noted that the drive controlling the Ex motor must always be installed in a separate ‘safe area’, even though the drive may be equipped with integrated safety functions which are certified and marked with ‘Ex’.

Getting to the desired safety level in the most cost efficient manner is highly dependent on selection of the right motors and drives. ABB has valuable knowledge in this area based on extensive experience with design, testing and certification for explosive atmospheres.

ABB today supplies numerous Ex-certified motors, and also offers a range of motor/drive combinations specifically tested and certified for safe operation in explosive environments. Process designers and engineers can therefore easily, and confidently, find the best motor/drive solution to keep people and property safe.

Variable combinations for total compatibility

To give even more flexibility in complying with safety standards, ABB’s all-compatible ACS880 industrial drives offer several good possibilities. The easiest is simply to use an integrated ABB drive/motor package which has been pre-tested, dimensioned and certified together, according to the IECEx and ATEX standards. This combination saves time and money for designers and users in terms of safety certification, reliability and simplicity.

Works easily with all types of motors

When combined with non-ABB motors, as well, the ACS880 drives family offers further distinct benefits. The optional integrated ATEX-certified thermistor protection module can safeguard any non-ABB motor working in explosive applications. So if the motor’s sensor indicates an over-temperature, the thermistor protection module will activate the SIL/PL certified safe torque off (STO) function of the drive, which is ATEX certified as Safe Disconnection Function. It then disables the control voltage on the drive output power semiconductors, thus preventing the inverter from generating any voltage to rotate the motor.

The thermistor protection module, together with the drive’s integrated STO function, forms the Safe Motor Temperature (SMT) function as defined in EN/IEC 61800-5-2. The drive indicates the SMT fault if it has been activated.

This ability to work with non-ABB motors is a real advantage because it allows users to meet safety standards when combining this drive with any motor, even though they have not been tested together. This option makes the ACS880 far less limiting when using any type of mixed drive/motor combinations. Therefore a non-ABB Ex motor combination with ACS880 drives is easy, as the thermistor protection module links the two seamlessly to keep the process safe. Before combining the drive with the motor, it simply has to be verified that the motor is designed to operate together with the drive.

Flexibility covering yesterday, today and tomorrow

Another very important benefit comes about when an older ABB industrial drive such as an ACS600 or ACS800 is to be replaced with an ACS880. This retrofit requires no testing as ABB’s industrial drives are fully compatible from an Ex motor perspective.
The end result is that installation, retrofitting and replacement has been made easier and more cost effective than ever via the ACS880 drives. They are truly all-compatible, not only with previous ABB industrial drives, but with a wide range of non-ABB motors as well. For all EPC designers, end-users, OEMs and distributors this means they get the highest degree of flexibility and safety for operation in explosive environments, long into the future.


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